JNS 5 (2015) 175-181
Synthesis Magnesium Hydroxide Nanoparticles and Cellulose AcetateMg(OH)2-MWCNT Nanocomposite
M. Ghorbanali a, A. Mohammadi b, R. Jalajerdi c*
Faculty of Graphic, Higher Education Institute of Art Allameh Bahrololoom, Boroujerd, Iran
a
b
c
Advertising Engineering BRS Academy, New York, USA
Young Researchers and Elite Club, Arak Branch, Islamic Azad University, Arak, Iran
Article history:
Received 11/04/2015
Accepted 19/05/2015
Published online 01/06/2015
Abstract
Mg(OH)2 nanoparticles were synthesized by a rapid microwave
reaction. The effect of sodium dodecyl sulfonate (SDS as anionic
surfactant) and cetyl tri-methyl ammonium bromide (CTAB as
Keywords:
Nanoparticles
Nanocomposite
Thermal Stability
Cellulose Acetate
cationic surfactant) on the morphology of magnesium hydroxide
nanostructures was investigated. Multi wall carbon nano tubes was
*Corresponding author:
E-mail address:.
[email protected]
Phone: +98 863256414
Fax: +98 863256414
acetate (CA) matrix was studied using thermo-gravimetric analysis
(TGA). Nanostructures were characterized by X-ray diffraction
organo-modified for better dispersion in cellulose acetate matrix. The
influence of Mg(OH)2 nanoparticles and modified multi wall carbon
nano tubes (MWCNT) on the thermal stability of the cellulose
(XRD), scanning electron microscopy (SEM) and Fourier transform
infrared (FT-IR) spectroscopy. Thermal decomposition of the
nanocomposites shift towards higher temperature in the presence of
Mg(OH)2 nanostructures. The enhancement of thermal stability of
nanocomposites is due to the endothermic decomposition of
Mg(OH)2 and release of water which dilutes combustible gases.
2015 JNS All rights reserved
1. Introduction
Applying of halogen-free flame retardants is
widespread due to the increasing concern about the
health and environmental risks [1-3]. One of the
most commonly used mineral flame retardants is
energy. Moreover, it releases non-flammable water
which dilutes highly flammable gases. Magnesium
hydroxide is used as halogen-free flame-retardant
for polymers. Mg(OH)2 can act also as a reinforcing
agent, flame retardant and smoke suppressant
magnesium hydroxide. As the temperature rises
magnesium hydroxide shows an endothermic
additive with low or zero emissions of toxic or
hazardous substances [1–5]. The main advantages
decomposes (1.356 kJ/g) around 330◦C and absorbs
of polymeric materials over many metal compounds
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are high toughness, corrosion resistance, low
the name of Nanocyl’s innovative Multiwall Carbon
density and thermal insulation. Improvement of the
flame retardancy and thermal stability of polymers
Nanotubes.
Scanning electron microscopy (SEM) images were
is a major challenge for extending their use for most
applications. One of the main drawback of
obtained using a LEO instrument (Model 1455VP).
Prior to taking images, the samples were coated by
magnesium hydroxide is that for effective flame
retardancy tests high loading levels are required to
a very thin layer of Au (BAL-TEC SCD 005 sputter
coater) to make the sample surface conducting
achieve the appropriate fire retardancy. Increasing
the loading of inorganic metal hydroxides will
obtain better contrast and prevent charge
accumulation. In UL-94 a bar shape specimen of
result in a significant decrease in physical
properties. The higher level of flame retardancy of
plastic 127 × 12.7 × 1.6 mm is positioned vertically
and held from the top. A Bunsen burner flame is
nanoparticles is due to their bigger surface to
volume fractions which let them disperse into the
applied to the specimen twice (10 s each). X-ray
diffraction (XRD) patterns were recorded by a
polymeric matrix homogeneously, and hence leads
to formation of a compact char during the
Philips X-ray diffractometer using Ni-filtered CuKα
radiation. For preparation of nanocomposite, a
combustion [6-11]. Cellulose acetate has been used
in a wide range of applications due to its particular
multi-wave ultrasonic generator (Bandeline MS 73)
equipped with a converter/transducer and titanium
advantages. It is a biodegradable polymer with
applications in photographic, paper coating,
oscillator operating at 20 kHz with a maximum
power output of 100 W was used for the ultrasonic
packaging films and adhesives. The physical and
chemical properties of nanoparticles are greatly
irradiation. The effect of nanostructure on flame
retardant properties has been considered using UL-
influenced by their shape and size distribution as
well as their agglomerated state and dispersion
94 test. In UL-94 a bar shape specimen of plastic
127 × 12.7 × 1.6 mm is positioned vertically and
property, which are strongly related to the
preparation process [12-17].. In this work a facile
held from the top. A Bunsen burner flame is
applied to the specimen twice (10 s each). A V-0
and rapid method for preparation of magnesium
hydroxide was used. Magnesium hydroxide and
classification is given to material that is
extinguished in less than 10 s after any flame
modified carbon nano tubes were then added to the
cellulose acetate in order to increase the thermal
application, drips of particles allowed as long as
they are not inflamed. A V-1 classification is
stability and flame retardancy.
received by a sample with maximum combustion
time < 30 s, drips of particles allowed as long as
2 Experimental
they are not inflamed. The sample is classified V-2
if it satisfies the combustion time criteria of V-1,
2.1 Materials and characterization
Mg(NO3)2 6H2O, ammonia, ethylene glycol, sodium
but flaming drips are allowed. Materials are ranked
dodecyl sulfonate (SDS), cetyl tri-methyl
ammonium bromide (CTAB) were purchased from
as N.C. in UL-94 tests when the maximum total
flaming time is above 50 s. The sample is classified
Merck and cellulose acetate (CA) from SigmaAldrich. All the chemicals were used as received
HB when slow burning on a horizontal specimen;
burning rate < 76 mm/min [14-17].
without further purifications. Nanocyl™ NC 7000 is
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R. Jalajerdi et al. / JNS 5(2015) 175-181
2.2. Synthesis of Mg(OH)2 nanoparticles
1g Mg(NO3)2 6H2O and 0.2 g of surfactant were
dissolved in ethylene glycol. 20 mL of ammonia (12
M), was slowly added into the solution under
microwave irradiation at 750 W (5 minutes, 40s on :
60s off). The white precipitate was centrifuged and
washed with distilled water to removing the
surfactant, and later dried at 70°C for 24h in a
vacuum dryer. These stages carried out for four
surfactant materials as synergetic additives including
CTAB and SDS.
Fig. 2. XRD pattern of Mg(OH)2 nanoparticles
2.3. Synthesis of CA-Mg(OH)2 nanocomposite
4 g of CA was dissolved in 15 mL of acetone and For preparation of samples for UL-94 test after
then Mg(OH)2 (0.8 g) and MWCNT (0.2) were stirring, the product was casted on a template with
dispersed in 5 mL of acetone with ultrasonic waves dimension 127 × 12.7 mm and after about 48 h of
(60W, 30 min). The dispersion of Mg(OH)2 was then solvent evaporation; the nanocomposite was placed
added slowly to the polymer solution. The solution in the vacuum oven for another 6 h for removal of
was mixed under stirring for 6 h.
residual traces of water. The final sheets for the test
are 127 × 12.7 × 1.6 mm in dimension (stay at oven
90 °C for 48 h) (Fig. 1).
3. Results and discussion
XRD pattern of Mg(OH)2 nanoparticles is shown in
Fig. 2. It is indexed as a pure hexagonal structure
with suitable agreement to literature value
(reference peaks are also depicted in the XRD
pattern, JCPDS card no. 78-0316, Space group: P3m1).
Fig. 1. Preparation of CA-Mg(OH)2 nanocomposite
178
Fig. 3. SEM images of nanoparticles synthesized by SDS
By applying sodium dodecyl sulfonate (SDS as an
anionic surfactant, Fig. 3) nanoparticles with
mediocre size of 30 nm were synthesized.
R. Jalajerdi et al. / JNS 5(2015) 175-181
Fig. 4. SEM images of Mg(OH)2 nanoparticles obtained
by CTAB
SEM images of Mg(OH)2 synthesized by different
surfactants cationic and anionic are shown in Fig. 34 respectively. By using cetyl tri-methyl ammonium
bromide (CTAB: as a cationic surfactant)
nanoparticles with average diameter of 15 nm were
obtained (Fig. 4). Surfactant as a capping agent lead
R. Jalajerdi et al. / JNS 5(2015) 175-181
179
to nucleation step becomes predominant compare to
TGA graphs of pure CA and CA-MWCNT-
growth stage.
SEM images of modified MWCNTs are shown in
Mg(OH)2 nanocomposite are illustrated in Fig. 6a
and 6b respectively. Regarding to curves thermal
Fig 5 that confirm diameter of carbon nanotubes are
less than 100 nm. Modified CNT were prepared by
decomposition of CA-MWCNT-Mg(OH)2 shifts
towards higher temperature in presence of metal
carboxylation of nanotubes by applying sulfuric acid
and nitric acid simultaneously.
hydroxide and onset degradation temperature was
increased in compare with pure polymer.
The enhancement of thermal stability of
nanocomposites is because of endothermic
decomposition of Mg(OH)2 that absorbs energy. It
simultaneously releases water which dilutes
combustible gases. Dispersed nano-tubes and
Mg(OH)2 have also a obstruction effect to decrease
product volatilization and thermal transport among
decomposition of the polymer. Adsorption of
polymer chains onto the surface of Mg(OH)2
nanoparticles and nano tubes results in a
confinement of the segmental motions and suppress
chain-transfer reactions [1-3]. Because of the
presence of magnesium hydroxide (endothermic
decomposition and absorbs energy) differential
thermal analysis of the nanocomposite shows
endothermic peaks [1].
Fig. 5. SEM images of MWCNT
Fig. 6. TGA graphs of (a) pure CA (b) CA-MWCNTMg(OH)2 nanocomposite
R. Jalajerdi et al. / JNS 5(2015) 175-181
180
Mg(OH)2 nanostructures were prepared by a rapid
In CA-MWCNT-Mg(OH)2, nanoparticles and
nanotubes have been appropriately distributed in
microwave method. The effect of various
surfactants such as SDS and CTAB on the
CA matrix and because of hydrogen bonds between
them a suitable barrier layer of nanoparticles is
morphology
nanostructures
formed.
nanoparticles and modified MWCNT were then
added to cellulose acetate matrix. The influence of
of
was
magnesium
investigated.
hydroxide
Mg(OH)2
the metal hydroxide on the thermal properties of
CA was studied using thermo-gravimetric analysis.
Thermal decomposition of the CA nanocomposite
shift towards higher temperature in the presence of
Mg(OH)2 nanoparticles. The increase in flame
retardancy of the nanocomposites is due to
endothermic decomposition of Mg(OH)2 and
release of water which dilutes combustible gases.
Mg(OH)2 and MWCNT have also obstruction effect
to decrease the polymer volatilization and heat
transport during decomposition of the polymer.
Fig. 7. FT-IR of Mg(OH)2 nanoparticles
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